Method of renovating used oil and systems containing same



Patented on8, 19 40 I. I i I I I UNITED STATES PATENT OFFICE METHOD OF RENOVATING USED OIL AN SYSTEMS CONTAINING SAME William G. Horsch, Woodbury, N. 1., assignor to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application March 12, 1938,

I Serial N0. 195,664

6 Claims. (Cl. 252- 63) This invention is directed to a novel method be accomplished without dismantling and in for the renovation of oils deteriorated by the formany cases .without withdrawal from service. mation of sludge during use as a dielectric in Other objects and advantages are in part obvious, transformers, or as a lubricant in turbines, or in and in part will appear later herein. similar use. It is also directed to a method The herein described novel process for the 5 whereby the equipment in which such oils have renovation of oil to its original, sludge-free 'conundergone deterioration may readily be cleansed dition after oxidation from prolonged service at of the products of such deterioration. moderate temperatures has resulted in the for- Oils used for the lubrication of turbines and mation of sludge, as well as for the cleaning in 0 the like, and as a dielectric element in transformsitu of the partially sludge-blocked passages of ers and other electrical equipment are prone to the equipment, is based upon the discovery that deterioration during use, which results in the forcertain materials have the power of rendering jmation of sludge, a portion of which remains the sludge soluble in the oil without impairing suspended in the oil, and another portion of the electrical,heat-removing, or lubricating propwhich is deposited in the equipment wherein the erties of the oil. The process herein disclosed oil was used, and especially in the small passages consists in adding to the oil, after an inexpensive provided for the circulation of the oil therein. and simple preliminary cleaning to remove water,

These sludges, formed by prolonged exposure to filterable sludge and the like, a small amount of oxidizing, conditions in the presence of catalytic certain materials as above described, which eflect metals, at low temperatures, are quite different complete solution of the remaining sludge in the 20 from those formed at high temperatures. These oil, altering it to a condition where it is not subsludges, formed usually at temperatures of about s'tantially prone. to'reprecipitate and not harm- 225-250" F., have different characteristics from ful to the function of the oil, and which also ensludges formed at temperatures above about 300 ables the renovated oil, when returned to the F., the low temperature sludges frequently being equipment from which it was removed, to clean 25 particularly diflicult of removal to renovate the the partially sludge-blocked passages thereof oil and permit its reuse. without interruption of service.

Former methods of renovating these oils have Materials for the purposes of this invention contemplated the removal of the oil from the must not onlyhave the power to increase the equipment, .followed by a mechanical removal of sludge-dissolving power of the oil, but must also 30 the -sludge as by filtration, settling, centrifuging, have certain other desirable properties. They or the like, with return of the oil to the equipmust be readily miscible with the oil, and must ment. These processes do not clean the equipnot difler sufliciently from it in boiling point to ment of sludge precipitated therein, except by the unduly alter its vapor pressure under conditions flushing action of the returned cleaned oil. of use nor to increase the fire hazard attendant 3 Cleaning of the equipment can be accomplished thereon. Equally important is the requirement only by taking the equipment out of service and that such materials, when added to oils in quandismantling it. In many cases, the sludge retities suflicient for the purposes of this invention, maining in the equipment contributes to a; more shall not materially alter the electrical, heat-rerapid deterioration of the cleaned oil. In most moving, and/or lubricating properties of the oil. 40

cases, the methods of cleaning the oil do not com- It has been found that these properties, coupletely remove the sludge, but rather remove only pled with a remarkable capacity for dissolving that portion of the sludge which is agglomerated sludge and rendering it innocuous, are possessed sufliciently to be removed, leaving much finely .by the materials diphenyl and diphenyl oxide.

divided sludge material in suspension to later This invention is based upon this discovery and 45 .agglomerate and deposit when the oil is returned is directed to the use of these materials for the to service. above-defined purpose, and to the method of It is an object of this invention to provide a cleaning such equipment by making use of these method whereby used oils of these classes may materials.

be cleaned of suspended sludge materials, and When up-to about 10% by weight of the abov 50 whereby such materials, otherwise unremoved, substance is added to a sludged turbine or transmay be rendered substantially incapable of reformer oil containing about 0.05 to 0.10% by precipitation. A further and important object is weight of suspended sludge and the mixture is the provision of a method whereby the cleaning heated to about 100 C., the sludge will be found 5 of the internal passages of theequipment may to dissolve to a substantially complete degree .mechanical separation of suspended sludge, wa-.

ter, and the likei'followed by addition of the said material which has high sludge-dissolving power; followed by return of the oil to the equipment. Such operations may, if desired, be-performed continuously in certain instances, or the continuous equipment installed for ordinary renovation of oils, as with some turbines, may be assisted by periodic additions to the renovated oils of the sludge-dissolving materials.- The sludge-dissolving material may, if desired, be

added to the oil in the form of a concentrated solution in fresh oil, which solution sometimes may be prepared conveniently with the aid of heat.

This invention also contemplates the internal cleaning or purging of the. equipment of sludge deposited in its interior and for this purpose makes use of the oil, renovatedby the above procedure, and .containing sludgedissolving'ma- 'terial in excess of that needed for the ordinary renovation. After the oil, so treated, has been returned to the equipment, as for instance a transformer, in a period of a few days, the exact time depending upon how high the temperature rises in service and how bad the sludge conditions are, the whole interior of the transformer v will become clean through the dissolving of the sludge.

As pointed out hereinbefore, it is usual and preferred to add to the deteriorated oil about 10% of its weight of the indicated compounds. More may be added if necessary, the upper limit being controlled either by the limit of solubility of the addivtive compound in the oil, or by the amount which may be added without seriously altering the necessary physical characteristic of. the oil.

I claim:

1. .Method of removing low-temperature sludge from dielectric mineral oil compositions comprising adding thereto a substance selected from the group consisting of diphenyl and diphenyloxide.

2.. Method of removing low-temperature sludge deposited in electrical'apparatus comprising'wetting the sludge with a dielectric mineral oil containing a substance selected from the group consisting of diphenyl and diphenyloxide.

3. Method of dissolving low-temperature sludge in a mineral oil dielectric comprising adding sisting of diphenyl and diphenyloxide.

4. Method fof, removing low-temperature sludge-like oxidation products from mineral oil dielectric compositions comprising dissolving therein a substance selected from the group consisting of diphenyl and diphenyloxide.

.thereto -a substance selected from the group con- 5. Method of removing sludge formed at tem- I peratures below about 300 F. in a mineral oil dielectric 'composition comprising dissolving therein a substance selected-from the group consisting of diphenyl'and diphenyloxide.

6. Method of removing low temperature sludge from a mineral oil dielectric while in use without interruption of service comprising dissolving in said dielectric a substance selected from the group consisting of diphenyl and diphenyloxide.

7 WILLIAM G. HORSCH. 

